Display system Timing Controller (TCON) electronics accept control and data from upstream graphics generation electronics and reformat them to fit the requirements of the row and column drivers used to drive displays. The Data Enable (DE) signal is the control mechanism used to indicate when graphics data is actively being transmitted to the TCON. The DE signal is active (logic one state) when data is being transmitted, and is inactive (logic zero state) during periods when no data is being transmitted. Periods of time in a horizontal line when data is not being transmitted is referred to as horizontal blanking. Lines within a graphics frame when data is not being transmitted are referred to as vertical blanking lines.
Some graphics generators, however, do not follow this protocol. Instead, they may send a false DE signal sometime during the vertical blanking period. Data driven during the false DE is not meant to be displayed.
Without a means to handle a false DE, a TCON may accept the false DE as a valid DE, and will not remain synchronized to the actual graphics data and control. This could result in undesired visual artifacts on the display, such as sections of missing data or data being scrolled down the screen.